Out of those three, I have to pick Burger King. Wendy's has never been that great in my opinion and McDonald's is just gross now that their fries are too salty instead of too fattening. Not to mention that McDonald's is just plain unhealthy. A McGriddle has like 400mg of cholesterol in it or something like that. @_@
I'll agree with whoever said that Carl's Jr. is bottom rung. I hate that place so much; their food is absolutely disgusting. Their breakfast biscuits would be good if they weren't so freaking greasy.
However, my two favorite fast food places are probably Taco Bell and Subway. Chili cheese burritos taste good and are cheap. XD Subway is kind of expensive, but it's a lot healthier and tastes pretty awesome. Subway Club on Honey Oat with olives, spinach leaves, ranch dressing and parmesan cheese. :d
Popeye's is good but I have to go about 10 miles to get to one now. They closed down the one in my town.
Sonic is also really good, but it's awfully pricey for fast food, unless you just get a regular burger, drink and fries or something. I like their breakfast Toaster sandwiches.